Handheld designers often grapple with ways to de-bounceand control the on/off pushbutton of portable devices.Traditional de-bounce designs use discrete logic, fl ipflops, resistors and capacitors. Other designs includean onboard microprocessor and discrete comparatorswhich continuously consume battery power. For highvoltage multicell battery applications, a high voltageLDO is needed to drive the low voltage devices. All thisextra circuitry not only increases required board spaceand design complexity, but also drains the battery whenthe handheld device is turned off. Linear Technology addressesthis pushbutton interface challenge with a pairof tiny pushbutton controllers.
上傳時間： 2013-11-18
上傳用戶：ZJX5201314
Piezoelectric motors are used in digital cameras for autofocus,zooming and optical image stabilization. Theyare relatively small, lightweight and effi cient, but theyalso require a complicated driving scheme. Traditionally,this challenge has been met with the use ofseparatecircuits, including a step-up converter and an oversizedgeneric full-bridge drive IC. The resulting high componentcount and large board space are especially problematicin the design of cameras for ever shrinking cell phones.The LT®3572 solves these problems by combining astep-up regulator and a dual full-bridge driver in a 4mm× 4mm QFN package. Figure 1 shows a typical LT3572Piezo motor drive circuit. A step-up converter is usedto generate 30V from a low voltage power source suchas a Li-Ion battery or any input power source within thepart’s wide input voltage range of 2.7V to 10V. The highoutput voltage of the step-up converter, adjustable upto 40V, is available for the drivers at the VOUT pin. Thedrivers operate in a full-bridge fashion, where the OUTAand OUTB pins are the same polarity as the PWMA andPWMB pins, respectively, and the OUTA and OUTB pinsare inverted from PWMA and PWMB, respectively. Thestep-up converter and both Piezo drivers have their ownshutdown control. Figure 2 shows a typical layout
上傳時間： 2013-11-18
上傳用戶：hulee
Alkaline batteries are convenient because they’re easy tofi nd and relatively inexpensive, making them the powersource of choice for portable instruments and devicesused for outdoor recreation. Their long shelf life alsomakes them an excellent choice for emergency equipmentthat may see infrequent use but must be ready to go on amoment’s notice. It is important that the DC/DC convertersin portable devices operate over the widest possiblebattery voltage range to extend battery run time, and thussave the user from frequent battery replacement.
上傳時間： 2014-12-24
上傳用戶：569342831
Avalanche photo diode (APD) receiver modules arewidely used in fi ber optic communication systems. AnAPD module contains the APD and a signal conditioningamplifi er, but is not completely self contained. It stillrequires signifi cant support circuitry including a highvoltage, low noise power supply and a precision currentmonitor to indicate the signal strength. The challenge issqueezing this support circuitry into applications withlimited board space. The LT®3482 addresses this challengeby integrating a monolithic DC/DC step-up converter andan accurate current monitor. The LT3482 can supportup to a 90V APD bias voltage, and the current monitorprovides better than 10% accuracy over four decades ofdynamic range (250nA to 2.5mA).
上傳時間： 2014-01-18
上傳用戶：wenyuoo
Automotive power systems are unforgiving electronicenvironments. Transients to 90V can occur when thenominal voltage range is 10V to 15V (ISO7637), along withbattery reversal in some cases. It’s fairly straightforwardto build automotive electronics around this system, butincreasingly end users want to operate portable electronics,such as GPS systems or music/video players,and to charge their Li-Ion batteries from the automotivebattery. To do so requires a compact, robust, effi cientand easy-to-design charging system
上傳時間： 2013-11-04
上傳用戶：wfl_yy
Many system designers need an easy way to producea negative 3.3V power supply. In systems that alreadyhave a transformer, one option is to swap out the existingtransformer with one that has an additional secondarywinding. The problem with this solution is that manysystems now use transformers that are standard, offthe-shelf components, and most designers want toavoid replacing a standard, qualifi ed transformer with acustom version. An easier alternative is to produce thelow negative voltage rail by stepping down an existingnegative rail. For example, if the system already employsan off-the-shelf transformer with two secondary windingsto produce ±12V, and a –3.3V rail is needed, a negativebuck converter can produce the –3.3V output from the–12V rail.
上傳時間： 2013-10-09
上傳用戶：Jerry_Chow
The LTC3546 is a dual output current mode buck regulatorwith fl exible output current partitioning. Beyondthe advantages normally associated with dual outputregulators (reduced size, cost, EMI and part count, withimproved effi ciency), the LTC3546’s outputs can bepartitioned for either 3A and 1A outputs, or two 2A outputs.This increases its application range and simplifi esmultiple supply rail designs. A confi gurable Burst Mode®clamp for each output sets the current transition levelbetween Burst Mode operation and forced continuousconduction mode to optimize effi ciency over the entireoutput range. An adjustable switching frequency up to4MHz and internal power MOSFET switches allow forsmall and compact footprints.
上傳時間： 2013-11-04
上傳用戶：yxgi5
The LTC®3610 is a high power monolithic synchronousstep-down DC/DC regulator that can deliver up to 12Aof continuous output current from a 4V to 24V (28Vmaximum) input supply. It is a member of a high currentmonolithic regulator family (see Table 1) that featuresintegrated low RDS(ON) N-channel top and bottomMOSFETs. This results in a high effi ciency and highpower density solution with few external components.This regulator family uses a constant on-time valleycurrent mode architecture that is capable of operatingat very low duty cycles at high frequency and with veryfast transient response. All are available in low profi le(0.9mm max) QFN packages.
上傳時間： 2013-11-07
上傳用戶：moerwang
The LTC®4151 is a high side power monitor that includesa 12-bit ADC for measuring current and voltage, as wellas the voltage on an auxiliary input. Data is read throughthe widely used I2C interface. An unusual feature in thisdevice is its 7V to 80V operating range, allowing it to coverapplications from 12V automotive to 48V telecom.
上傳時間： 2013-10-29
上傳用戶：集美慧
Once relegated to the hinterlands of low cost indicatorlights, the LED is again in the spotlight of the lightingworld. LED lighting is now ubiquitous, from car headlightsto USB-powered lava lamps. Car headlights exemplifyapplications that capitalize on the LED’s clear advantages—unwavering high quality light output, tough-assteelrobustness, inherent high effi ciency—while a USBlava lamp exemplifi es applications where only LEDs work.Despite these clear advantages, their requirement forregulated voltage and current make LED driver circuitsmore complex than the venerable light bulb, but some newdevices are closing the gap. For instance, the LTM®8040μModule™ LED driver integrates all the driver circuitryinto a single package, allowing designers to refocus theirtime and effort on the details of lighting design criticalto a product’s success.
上傳時間： 2013-10-16
上傳用戶：togetsomething
